1. Technical Field
The invention relates to automatic self-guiding vehicles and in particular to an automatic self-guiding lawn mower and mowing method. More particularly, the invention relates to such an automatic lawn mower which guides itself along a peripheral edge of an area of uncut grass without becoming confused by conditions such as bare spots in the lawn.
2. Background Information
Landscaping is very important to the overall beauty and value of most homes. One of the most important components of the landscaping of many homes is a well-manicured lawn. Large amounts of time, effort and expense are involved in developing and maintaining a nice lawn, and includes such tasks as application of fertilizers and weed and insect killers at regular intervals, watering during dry periods, and mowing. The most tedious of these tasks is mowing. Depending on geographical location and weather trends such as rainfall and temperature, it generally is necessary to mow a lawn on a weekly basis during the growing season, which spans at least six months in most areas of the United States. Depending on the size of a particular lawn and the mowing equipment available, this task can take from minutes to hours.
Technology does exist, over and above usual push mowers having engine-powered cutting blades, to decrease the time it takes to mow a lawn. For example, riding mowers and self-propelled hand mowers can significantly reduce the time and effort involved in mowing a lawn. However, many individuals still do not mow their own lawns for numerous reasons, such as physical disability, lack of time, or laziness. For these individuals, even riding mowers and self-propelled hand mowers often do not provide a satisfactory solution.
Thus, landscape companies offering complete landscape maintenance services including lawn mowing have found a stable niche in our economy. The number of successful landscape companies continues to increase with such increase possibly being attributable to the growing complexity of our society, where people seem to have less time to get things done, including mowing their lawns. However, persons wishing to hire a landscape company can expect to pay from several hundred to a thousand dollars or more just for an annual lawn mowing service, absent any other specialized landscaping services such as a fertilization program, plant maintenance, etc.
Attempts have been made to develop a lawn mower which is advanced over riding mowers and self-propelled hand mowers, and which provides a viable alternative to expensive landscape service companies for those individuals who do not mow their own lawns. The known prior art discloses numerous self-guiding lawn mowers in U.S. Pat. Nos. 3,425,197; 3,924,389; 4,184,559; 4,545,453; 4,573,547; and 4,603,753; and a self-guiding farm tractor in U.S. Pat. No. 3,583,514. However, the equipment disclosed in each of these patents is constructed and operates in a completely different manner than our improved automatic self-guiding lawn mower.
Specifically, our invention utilizes a plurality of cutting blades each driven by a motor having a power consumption sensing device attached thereto, which detects a difference in power consumption by its respective motor depending on whether the attached blade is traveling through cut or uncut grass. These sensors then cause actuation of certain of the various motors which drive the wheels of the mower or reversal of the polarity of the wheel motors and direction of the mower, for directing the mower along a peripheral edge of an area of uncut grass. Trimmer potentiometers also are incorporated into the motor drive circuits to provide fine control and adjustment for the individual motors. In contrast, the prior art apparatus disclosed in the above-listed patents use photosensors coupled with geomagnetic sensors, sensor brushes, sensor blades, or electric current sensors, for guidance. However, some of these guidance systems can be confused causing undesirable results. For example, electric current sensors and sensor brushes can be fooled by bare spots in a lawn.
Other known prior art of interest includes U.S. Pat. No. 3,548,570 which discloses a vehicle-carried, hydraulic powered blade for cutting sugar cane, the height of which is automatically adjusted by a sensor in response to changes in the hydraulic fluid pressure caused by resistance against the blade when it strikes the ground and cane. U.S. Pat. No. 4,513,562 suggests monitoring the loading of a combine harvester for regulating the ground speed thereof which in turn controls the amount of crop being loaded to prevent clogging, by sensing the power consumption of the cutting sickle of the combine. However, the structure, operation and results achieved by our improved lawn mower of the present invention are different than those disclosed in the above patents.
Thus, the need exists for an improved self-guiding lawn mower and mowing method for automatically mowing a lawn without confusion of the mower by conditions such as bare spots in the lawn, grass clippings, etc.